1. Field of the Invention
The present invention relates to a font compression method and apparatus which are capable of advantageously compressing a font of characters and figures or patterns expressed by dots, without deterioration of the original characters and patterns.
2. Description of the Prior Art
It is a normal practice to form a font of characters by data in a 24.times.24 dot matrix, when displaying and printing, for instance, characters by means of a personal computer and a word processor. However, the print of many of these output units including dot printers normally consists of a 16.times.16 dot matrix. Accordingly, when using these output units, it is necessary to compress a 24.times.24 dot matrix font into a 16.times.16 dot matrix font. In this case, the method of compression according to the prior art was to uniformly extract dots in such a manner that one dot for every two dots is dropped or deleted from the 24.times.24 dot matrix when converting it into a 16.times.16 dot matrix. This compression method according to the prior art has a major disadvantage. That is, relatively wide spaced portions which separate lines of characters and figures and portions between the lines are expressed by a plurality of dots of the same kind arranged successively. These lines and spaced portions do not affect the features of characters and patterns, even if the length of the lines is shortened or the size of the spaced portions is made small by dropping or deleting some dots. On the other hand, with respect to a spot of a character or figure, or a relatively narrow spaced portion expressed by a single dot, the form of the character and the figure is deformed if the single dot is dropped or the spaced portion is lost. Accordingly, when a font is to be compressed, it is preferable to compress from lines and relatively wide spaced portions of characters and figures. This is not done in the prior art.
Moreover, when a font of the characters and patterns is compressed such that it is unbalanced, e.g. when it is compressed mostly, for instance, in the right portion of the characters with the left portion being seldom compressed or almost without compression, the form of the characters is also deformed. Accordingly, it is necessary to compress the font in a uniform or balanced condition by dropping the most suitable dots from each portion of the font.
In the font compression method according to the prior art, however, as information bits to be dropped are not necessarily suitable, the font after compression is deformed in such a way that vertical and horizontal lines of the characters and figures are often split or the lines of characters and figures often merge with each other, thus making read-out of these characters extremely difficult.